The present invention relates to a catheter such as an angiographic catheter for use in an image formation of the heart or of tissues on the periphery thereof and a catheter for injecting a liquid medicine into a desired part of a human body.
As well known, including coronary angiography for checking the state of the blood vessel of the heart, a selective angiography for checking the states of blood vessels has been performed by injecting a contrast medium into branch portions of the blood vessels through a catheter, with the front end thereof inserted thereinto. For example, as catheters for use in the coronary angiography, a Judkins type catheter and an Amplatz type catheter are known. Normally, these catheters are introduced into the blood vessel from the femoral artery by a Seldinger method or a sheath method to perform selective coronary angiography.
In this case, some catheters are used for the angiography of the right coronary artery only, while other catheters are used for the angiography of the left coronary artery only. In recent years, a catheter which can be used for the angiography of both the right and left coronary arteries has been developed and is in use.
In the case the catheter for use in the angiography, a type having a side aperture formed at the front end thereof and a type not having a side aperture formed at the front end thereof are used.
In the catheter having the side aperture formed at the front end thereof, blood flows into the catheter from the side aperture. Thus, the pressure inside the catheter is maintained at an approximately constant pressure. Therefore, the catheter of this type has an advantage that when the front end of the catheter is inserted deep into the coronary artery, it is possible to prevent the inside of the catheter from becoming almost vacuum. Thus, it does not occur that it is difficult to pull the catheter from the coronary artery, i.e., it does not occur that the catheter is wedged in the coronary artery. Further, when a contrast medium is jetted to a desired blood vessel part under a high pressure from the front end of the catheter, a part of the contrast medium leaks out from the side aperture. Thus, the contrast medium is jetted out from the front end of the catheter at a reduced speed. Therefore, it is possible to prevent the front end of the catheter from being dislocated from a blood vessel branch portion at the time of the coronary angiography (at the time of injection of contrast medium).
However, the side aperture of the conventional catheter is open at a right angle with the axial direction of the catheter. Thus, it often occurs that the contrast medium discharged from the side aperture does not flow into a desired blood vessel part but often leaks downstream from the blood vessel branch portion. Consequently, a small absolute amount of the contrast medium flows to the desired blood vessel part. That is, the conventional catheter has a low degree of angiographic performance.
In the catheter not having the side aperture formed at the front end thereof, the contrast medium is all jetted toward a desired blood vessel part. But the contrast medium is jetted from the front end of the catheter at a high speed. Thus, a portion having a pressure higher than a pressure-jetted portion is generated forward from the pressure-jetted portion, and hence the contrast medium flows backward therefrom to the blood vessel branch portion. Consequently, the contrast medium does not flow into the desired blood vessel part but leaks downstream from the blood vessel branch portion. In order to enhance the angiographic performance of the catheter, it is necessary to flow the contrast medium more to the desired blood vessel part at a higher pressure because of the contrast medium has leaked. In this case, it is very likely that the front end of the catheter is dislocated from the blood vessel branch portion during the angiographic operation.
The smaller the diameter of the catheter is, the smaller is the diameter of the stream of the contrast medium discharged from the front end of the catheter. Thus, it is difficult to form the image of the inlet of the coronary artery (blood vessel branch portion). In order to form the image of the inlet of the coronary artery reliably, the injection pressure (discharge pressure) of the contrast medium is raised to increase the backward flow amount of the contrast medium.
As described above, when the catheter having the side aperture formed at the front end thereof is used, it often occurs that the contrast medium discharged from the side aperture does not flow into the desired blood vessel part. When the catheter not having the side aperture formed at the front end thereof is used, the contrast medium discharged from the front end thereof flows backward because the contrast medium is jetted from the front end thereof at a high speed. That is, the catheter of each of both types does not provide reliable angiographic performance. Thus, there is a growing demand for the development of a catheter capable of solving the problems of the catheter of both types and having reliable angiographic performance.
It is an object of the present invention to provide a catheter capable of jetting a liquid from the front end thereof at a low speed, preventing the front end thereof from being dislocated from a blood vessel branch portion, preventing the liquid from flowing backward, and reducing the amount of the liquid which leaks from a desired part.
It is another object of the present invention to provide a catheter capable of jetting a contrast medium from the front end thereof at a low speed, preventing the front end thereof from being dislocated from a blood vessel branch portion, preventing the contrast medium from flowing backward, reducing the amount of the contrast medium which leaks from a desired part whose image is to be formed, and being reliable in an image formation performance. The catheter which achieves the above object is, for example, an angiographic catheter for use in coronary angiography or the like for performing a selective image formation by inserting a front end thereof into a branch portion of a blood vessel.
It is still another object of the present invention to provide a catheter capable of forming the image of an inlet of the coronary artery securely, without injecting a contrast medium to a desired part at a high pressure.
The catheter of the present invention has a tube body having a lumen, a front end opening communicating with the lumen, and a side aperture communicating with the lumen. The side aperture is obliquely formed from an inner peripheral surface of the tube body toward an outer peripheral surface thereof such that the side aperture is directed toward a front side of the tube body.